Sun xVM VirtualBox is an x86 virtualization software package originally create by German software company innotek GmbH that is now being developed by Sun Microsystems, Inc. It is installed on an existing host operating system; within this application, additional operating systems, each known as a Guest OS, can be loaded and run, each with its own virtual environment. For example, several Linux distributions can be guest hosted on a single virtual machine running Windows XP as the Host OS; or, XP and Windows Vista can run as guest OSes on a machine running OpenSolaris, Solaris or Linux.